Electron tube



July 8, 1941. w, UHLMANN 2,248,795

ELECTRON TUBE Filed July 18, 1939 Mayra/22 [Ml/0mm.

Patented July 8, 1941 iJNiTiZiJ ELECTRON TUBE A iplication July 18,1939, Serial No. 285,047 In Germany July 19, 1938 2 Claims.

In electron tubes or cathode ray tubes the electrode system hasheretofore been scaled as a whole into the vessel thereof. This methodhas the disadvantage that in the case of exchanging the cathode, whichin general is of less durability than any other of the electrodes, theentire electrode system must be sealed afresh. In order to overcome thisdrawback the invention proposes to fix the cathode on the one hand andthe assembly of the other electrodes on the other hand in dilferentportions of the vessel.

The drawing shows a diagrammatic sectional View of one embodiment of theinvention. Fig. 1 is a sectional view of a side elevation of a tubeconstructed in accordance with my invention; Fig. 2 shows an end view ofthe tube.

The leads or wires I for the electrode system 2 except the cathode 3 arein an annular row fastened in a reduced portion or neck b of the vacuumvessel t. The cathode 3 is mounted in well known manner in a stem 5sealed to a tubular extension 9 of the neck 1). Sealed to the tubularextension 9 is also the well known sealing-off or exhaust tube 6, whichis fixed thereto in conjunction with the stem 5.

According to a further part of the invention the following method ofmanufacture is proposed. From the neck 11 a portion is cut off in amanner to form an annular surface or edge 0. Edge 0 is covered withsealing glass 11. By means of the glass 01 and of glass e provided onthe leads or wires i these are provisionally sealed to the edge 0.Hereupon tube 9, one end of which carries sealing glass f, is with thisend inserted in the neck 13. Finally the tube g, edge e and the wires lare sealed and blown together with the aid of the vitreous materials d,e, 1.

According to one mode of assembly the electrode system 2 may first bemounted on a sort of base plate which has a comparatively wide tubefixed in the middle thereof. This tube serves for inserting afterwardsthe cathode. Such base plate, carrying the electrode system 2, is thensealed into the neck b. Finally, the stem 5, in which the cathode 3 ismounted, the tubular extension 9 and the exhaust tube 6 are sealed toether.

(Cl. {Mid-27.5)

The novel method presents the following advantages: When fixing theelectrode system 2, this step of manufacture requiring the use oftemperatures higher than in the case of the coated cathode, the latteris not yet within the vacuum vessel so that the diiiicult step ofmounting the system 2 may be effected without regard to theheat-sensitive cathode. Also, if the seals by which the wires l are heldin place prove not to be tight they may be reheated without affect ingthe cathode, since this and the stem 5 are not arranged until the wiresl have been sealed in position. In order to provide convenient means ioradjusting the correct distance between cathode and Wehnelt cylinder 1,the cathode may be fitted with a ceramic member D which is inserted inthe cylinder l until it comes against stops E which are angular piecesmade of sheet metal and welded to cylinder 1.

The sealing spot of the stem 5 is so small and so far remote from thepaste layer of the cathode that this layer will not be subject todetrimental temperatures.

What is claimed is:

1. An electron tube comprising a vessel, a cathode, a stem carrying thiscathode independently of other electrodes in said tube, a tubularextension formed with this stem, a plurality of electrodes supportedmechanically independently of said cathode and having leads arranged inan annular row, said tubular extension being sealed to said annular rowof leads, and an exhaust tube formed with said tubular extension.

2. In the manufacture of electron tubes having a vessel with a reducedend portion, the method which consists in cutting a cylindrical piecefrom this end portion so as to form thereon an annular edge, providingthis edge with sealing glass, fixing electrode leads to this glass,sealing a tubular extension to the said annular edge and leads, andfinally sealing a stem having a cathode mounted thereon together with anexhaust tube to this tubular extension.

WOLFRAM UHLMANN.

